Presentations

Abstract

In an event-related fMRI study, we investigated to what extent semantic and
referential aspects of language comprehension recruit common or dis-
tinct neural ensembles. We compared BOLD responses to sentences containing semantically anomalous or coherent words, and to sentences containing referentially ambiguous pronouns (e.g., “Ronald told Frank that he...”), referentially failing pronouns (e.g., “Rose told Emily that he...”) or coherent pronouns. Semantic anomaly elicited activation increases in lateral prefrontal brain regions associated with semantic pro-
cessing. Referential failure elicited
activation increases in brain regions
associated with morphosyntactic processing, and additional activations
associated with elaborative inferenc
ing if readers took failing pronouns
to refer to unmentioned entities. Referential ambiguity selectively
recruited medial prefrontal regions,
suggesting that readers engaged in
problem-solving to select a unique
referent from the discourse model.
Furthermore, our results showed that semantic anomaly and referential
ambiguity recruit overlapping neural ensembles in opposite directions,
possibly reflecting the dynamic re
cruitment of semantic and episodic
processing to resolve semantically or referentially problematic situations.
These findings suggest that neurocogni
tive accounts of language compre-
hension will have to address not just how we parse a sentence and com-
bine individual word meanings, bu
t also how we determine who’s who
and what’s what during sentence and discourse comprehension

Abstract

In this event-related brain potentials (E RP) study, we explored the possibility to selectively track referential ambiguity during spoken discourse comprehension. Earlier ERP research has shown that referentially am biguous nouns (e.g., “the girl” in a two-girl context) elicit a frontal, sustained negative sh ift relative to unambiguous control words. In the current study, we examined whether this ERP effect reflec ts ‘deep’ situation model ambiguity or ‘superficial’ textbase am biguity. We contrast ed these different interpretations by investigating whether a discourse-level semantic manipulation that prevents referential ambiguity also averts t he elicitation of a referentially induced ERP effect. We compared ERPs el icited by nouns that were re ferentially non-ambiguous but were associated with two discourse entities (e .g., “the girl” with two girls introduced in the context, but one of which has died or le ft the scene), with referentially ambiguous and non-ambiguous control words. While temporally referentially ambiguous nouns elicited a frontal negative shift compared to control words, the ‘double bo und’ but referentially non-ambiguous nouns did not. These results suggest that it is possible to selectively track referential ambiguity with ERPs at the level that is most relev ant to discourse comprehension, the situation model

Abstract

In general, language comprehension is surprisingly reliable. Listeners very rapidly extract meaning from the unfolding speech signal, on a word-by-word basis, and usually successfully. Research on ‘semantic illusions’ however suggests that under certain conditions, people fail to notice that the linguistic input simply doesn’t make sense. In the current event-related brain potentials (ERP) study we examined whether listeners would spontaneously detect an anomaly in which a human character central to the story at hand (e.g. “a tourist”) was suddenly replaced by an inanimate object (e.g. “a suitcase”). Because this replacement introduced a very powerful coherence break, we expected listeners to immediately notice the anomaly and generate the standard ERP effect associated with incoherent language, the N400 effect. However, instead of the standard N400 effect, anomalous words elicited a differential ERP effect from about 500-700 ms onwards. The absence of an N400 effect indicates that subjects did not immediately notice the anomaly, and that for a few hundred milliseconds the comprehension system has converged on an apparently coherent but factually incorrect interpretation. The presence of the later ERP effect indicates that subjects were processing for comprehension and did ultimately detect the anomaly. Therefore, we take our results to reflect a temporary semantic illusion. Our results also show that even attentive listeners sometimes fail to notice a radical change in the nature of a story character, and therefore demonstrate a case of short-lived ‘change deafness’ in language comprehension.

Abstract

n two ERP-experiments we examined whether discourse context could overrule a local semantic violation. In both experiments, subjects listened to stories in which a person was engaged in conversation with an inanimate object. In experiment 1, story-initial animacy violations reflected in an N400 effect were completely neutralized further down the story. In experiment 2, canonical but story-irrelevant inanimate predicates assigned to the inanimate object elicited an N400 effect, compared to contextually appropriate animate predicates.